The
circular patterns A and B below
may spin if you slide a grid (a transparent
overlay pattern representing vertical stripes)
across them!

Pattern
A

Vertical
stripes

Example
in motion

Pattern
B (variant of A)

Vertical
stripes

Example
in motion

Another
curious example of optical motion
with static imagesThe image below represents a printed card
with a curious design consisting of a collection of vertical
lines. These lines contain information about six different
images, that together form an animation ('Dancing Man').
As a green grid is slid to and fro, different selections
of lines become visible, and the animation appears!

These
cards, called Kineticards, have different designs
(currently these are only available from the artist)Eye
Think, Inc.
971 Commonwealth Ave.
Boston, MA 02215

The trapezoid
window illusion shows that our perceptions
do not always give us correct information about
the physical stimulus. When the trapezoid window
is in continuous rotation and it is observed with
one eye only, it seems to move back and forth like
a pendulum (while in reality it is spinning round
and round!). This occurs because the brain is interpreting
the longer side of the trapezoid as being closer,
and the shorter side as being farther away, even
when they are not! (When the longer side is really
farther away, we mistakenly see it as closer, just
like the closer side of a moving rectangle)